Pickup mounting



C. E. KILGOUR PICKUP MOUNTING June 6, 1950 Filed -April 5, 1946INVENTOR.

Patented June 6, 1950 UNITED STATES PATENT OFFICE PICKUP MOUNTINGCharles E. Kilgour, Cincinnati, Ohio, assigner, by niesne assignments,te AVGO Manufacturing corporation, .a corporation of DelawareApplication April 3, 1946, Serial No. 659,215

' This invention relates to phonograph reproduction and is particularlyconcerned with the reproduction oi sound from laterally cut diskrecords. While the invention is illustrated in connection withreproduction through a piezo-electric crystal, it can be availed of inconnection with other types of pick-ups such as those that establish avariable magnetic iield or a variable intensity of light from whichsuitable variations in electric current are derived.

The invention is specifically concerned with a method of and means formounting the pick-up means, e. g., a pick-up cartridge, in a tone armand the construction of a motion transferring device by which themodulations in the grooves in a phonograph record are transferred to thepick-up.

In the reproduction of sound from a phonograph record by means of a`pick-up generating an electrical signal which is amplified andimpressed upon a translation device such as a loud speaker to producesound, a certain amount of sound is produced directly by the vibrationof the 'pick up and associated structure. This is called .acousticradiation and is a fault that yhas been magnied by mounting the pick upin the tone arm by means which permits these sound waves to travel intothe tone arm and radiate therefrein, With customary types of apparatus,this direct radiation of sound may be of considerable magnitude and ofdistorted quality so as to be gri-ite annoying to the listener,,especially when the electrically produced sound iS adjusted to a lowvolume level. l have discovered that this radiation of sound (needlenoise) may be substane tially reduced in loulness when the pick-up ismechanically isolated from the tone arm. This isolation may :be effectedby sus-pending the pickup iroiu the tou@ arm by yielding,non=conductins, non-resonant means such as fabric or felt.

Where, for example, a crystal pickeup is used,

, it `.is possible to hang the pick-up cartridge from weights so as to.exert a lifting v.force .upon the cartridge. vIn this case, thestructural member er members connecting the arm and cartridge aresubjected to tensile stresses only so that cords or other flexibleSupports may be used..

With the vcoininonly used disk record, with a spiral groove.. it isnecessary for the Cartridge to exert enough lateral pressure en the tonearm to it to Swing horizontally .and follow the groove This result ,mayhe accomplished by the type of .Support describes above. The supporting2 Claims. (Cl. ZTL-24) tension `members will swing slightly out ofvertical alignment so that the horizontal component of their stress issuflicient to move the arm. Any tendency toward misalignment may bereduced by an increase in the tension of the supporting members whichmay be 'brought about by an increase in the difference between thecartridge weight and the needle pressure. Stability of the cartridge invertical alignment may be enhanced by an increase in the verticaldistance between the center of gravity of the cartridge and the point ofconnection of the flexible supporting member and the rigid cartridge.

An important object of the invention is the ref duction of acousticradiation or needle noise.

Another object is to reduce wear on phonograph records.

Another object is to organize the components of a sound reproductionsystem so that undesired high frequency responses or peaks areeliminated.

-The novel'features that I consider characteristic of the invention areset forth in the appended claims. The invention, itself, however, bothas to its organization and its method of operation, to, gether withadditional objects and advantages thereof, will best be understoood fromthe follow-.- ing description of specific embodiments when read inconjunction with the `accompanying drawings, in which-f Fig. l is a sideelevation with parts and a sec.- tion of a tone arm in which thefeatures of the in@ vention are incorporateda Fig. 2 is a section takenalong line -Zfz o f Fig. ,1:

Fig 3 is a section taken along line 3 3 of 1;

Fig. 4 is a section similar to Fig. 3 showing .a modiiied-form of thedevice;

Fig. v5 is a IOngitudinal section with 'the parts cut away of anotherdevice embodying the invention;

Fig. 6 is a section along line 6-6 of Fig. 5;

Fig. l is a section along line 1--1 of Fig. y,5;

Fig. ,3 is a fragmentary section taken longi-1 tudinally of a tone armshowing another way in which the principles of the invention may heutilized.

Fig. 9 is a section along line 9-9 of Fig. :8;

Fig. 10 is a fragmentary section showing lhow the pick-up cartridge maybe isolated in still other way;

Fig. l1 is a bottom view of the device shown in Fig. l0 lwith thephonograph stylus and its associated members removed.

Fig. 12 and Fig. 13 are sections taken respectively along lines |2-l2and I'3fl3 of Fig. 10.

Fig. 114, Fig. 15 and Fig. V16 are elevation, end and plan viewsrespectively .of an assembly Icy which a permanent point stylus orneedle maybe connected to a pick-up cartridge.

In Figs. 1 to 3 a tone larm In is provided with down-turned sides H andl2, and at the .end

thereof a motion translating means I3 such as a crystal cartridge ismounted in the manner hereinafter described. At the other` end of thetone arm is provided a reinforcing bracket I4 secured to the upper sideof the arm and this bracket has down-turned ears I5 having openings toreceive a pivot I5 supported in a member il that is mounted on thesleeve I8. As will be recognized, this illustrates a more or lessstandard form of construction in which the tone arm is mountedso that itmay be moved in a horizontal plane by a record changing mechanism thatturns sleeve IB at predetermined intervals.

In order to balance the weight of the device at the other end of thetone arm, a spring l5 may be tension-d between` lug 23, secured tomember I'I, and an extension 25 on one of the ears l5 of member I4. Thistends to cause theotherend of the tone arm to move upwardly about thepivot I6.

An adjustable screw 2! is secured to member I4 at a point opposite apush rod 22 'connected to the record changing mechanism. As is wellknown in the art, the rod 22 periodically rises to lift the tone arm sothat the 'stylus mounting device 5E! carrying the stylus or needle 33 isdisengaged frcm the record. y

In Figs. 1 and 3, the crystal cartridge is mounted by hanging the sameo'n ilegible cords 25. Each end of the cartridge is carried by as'tirrup 25 that can be snapped into place and each stirrup is providedcentrally with a boss 21 'in which is provided a suitable opening. Studs29 may be secured in the top of the tone arm and the cords 23 therebyadjustably secured in position as shown in the iigur'es. As shown, thelower ends of the cords are knotted in order to hold them in placeagainst the under side of the openings in bosses 21.

In Fig. 4 an illustrative form of the invention is shown with fourcords, 28a and 25h, two along each longitudinal edge of the cartridge,Only two of these four are shown in this figure. These may be secured tothe cartridge by knotting the ends through openings provided in stirrupsor holding 'members Similar to those shown in Fig. 3, and knotting theupper ends through openings in the upper side of the tone arm.

The cords 28a and 28h may consist oi' any suitable lexible, noneresonantmaterial incapable of transmitting sound vibrations and capable ofmechanically isolating the cartridge from the tone arm. They may be ofelastic material such as rubber.

In Fig. 1 a stylus mounting 3e is shown by means of which a stylus'.I 33is mounted in the cartridge I3. A knurled screw 3l is provided by whichthe shank of the stylus mounting means is held in a suitable chuck (notshown) provided in the cartridge. A weight 32 may be provided on theunder side of the cartridge if desired in order to obtain properrelationships between tension on the cords, the weight of the cartridgeand the force exerted against the needle by the record.

In order to increase the alignment stability of the cartridge, the sidesI I 'and I 2 of the tone arm may be provided with yieldable non-resonantmaterial such as soft felt to limit sideward movement of the cartridgeand restrain it from swinging an inordinate amount. Such a structure isshown in Figs. 5, 6 and '7, in which a 'cartridge I3@ is suspended bycords 28e and 28d. Flat springs 35 and 3l may be provided on the underside of the tone arm, and spring clips 38 and'59 may be secured to thecartridge by studs 4B by which the cord length may be conveniently ad-`iusted. v

In Figure 5, a weight 32a may be secured to the bottom of the cartridgeby studs 4I, the

Aweights having slots 42 for the purpose of facilitating adjustment.

The yieldable non-resonant material referred to above may be constitutedof soft felt pads 43 and 44, one on each oi the downwardly extendingsides! i and i2 of the tone arm. As has been indicated, these preventthe cartridge from swinging 'out' of position, yet insure maximummechanical isolation from the tone arm. The stylus mounting 3Q issecured in chuck (not shown) by knurled screw 45.

In Figs. 8 and 9, a modied construction' is shown, in which the upperpart of the tone arm is provided with depressions 50 and 5I, adapted andarranged to hold washers 52 and 53 of yield'- able, non-resonantmaterial, such as soit felt, having the capability `of isolating thecartridge from the tone arm. As shown, the material of the tone ar'm iscut away a substantial e'Xtent in order to permit studs 54 and 55 to beextended through the arm without mechanical contact therewith.Additional washers 55 and 51 are provided on the under side of the tonearm. These may be cemented to the arm and to the cartridge in order thatthe cartridge may hang on the arm, in which case studs 54 and 55 shouldnot be drawn up against washers 52 and 53. The studs are simply insertedinto suitable threaded openings in or attached to the cartridge |35 witha felt isolating means disposed on each side of the arm in the mannerShown. Relatively stii washers 58 and 59 may be provided to distributethe weight of the cartridge on the top Washers 52 and 53. A housing 49of light metal or plastic may be provided around the end of the tone armin order to preserve a neat appearance and to provide an additionalspace 48 to retard the direct radiation of sound.

In Figs. 10 to 13, still another embodiment of the invention is shown.In this embodiment, the cartridge 43C is oated in yieldingnon-conducting, non-resonant material such as felt and makes no contactdirectly with the tone arm. A bent member 55 is formed enclosing thefront end of the cartridge and is provided with an enlargement 5! whichfits into an opening in the front end of the tone arm. Member Si) withenlargement 5l holds the front end of the cartridge in place in the tonearm in cooperation with felt members S2, Si and 6?. A spring clamp 63holds the rear end of the' cartridge between felt members'z and 54 undera minimum amount ci compression. Soldering lugs or leads 65 and 66secured to cartridge I 3c aiiord a good base upon which the feltsupporting members may grip.

The member 50 is isolated from the cartridge Isc by the front end of thefelt member 54 which preferably extends around the end of the cartridge,and from the tone arm by a felt member 51, the sides of which follow theinside contour of the tone arm to isolate it laterally from thecartridge. The cartridge may be cemented to felt 64 and member 61 may becemented to 64 and H, as at 12, 73 and 14.

The stylus mounting means 35 is secured in the cartridge by insertingits shank through chuck l and holding it there Iby screw 1I.

In Figs. 14, i5 and 16 I have shown a stylus mounting assemblyparticularly well adapted for use 'with the present invention in that itreduces needle scratch and other high frequency vibra.-

tions and tends to prevent them from resonating with the cartridgeassembly. This stylus assembly is shown in my copending divisionalapplication Serial No. 84,899, filed April 1, 1949, entitled Stylusmounting for sound reproducer and assigned to the same assignee as thepresent application and invention. This comprises a shank 15 having anend 1B ibent at approximately the angle shown. The under side of thebent end 16 has bosses 11 adapted to be swaged over to hold springmember 18 securely against the over turned end 16. Spring member 18 hasnotches 80 in its sides that closely fit around the sides of the bossesand conform to their contours. Spring member 18 may conveniently be madeof resilient springy material such as beryllium bronze.

The other end of the spring 18 is provided with an opening 19 in which apermanent point stylus such as a sapphire 33 is press fitted. A dampingmember 8| is provided along one side, preferably the upper side of thespring member 1'8. Member 8| is cemented or otherwise secured along thewhole upper surface of member 18 and is extended horizontally, as in theform of heart shaped lobes 82` and 83. The mass of member 8| is thusspread out and distributed in a horizontal plane rather than beingconcentrated at one point. The construction, conguration and mass of thedamping material 8| and its distribution over the surface oi spring 18is such that a very eiective damping of peak resonances at the highfrequency end of the audio range is achieved. Member 8| may beconveniently made of any suitable damping material such as a plasticizedCelluloid. y

In order to maintain the bending stress uniform throughout its length,the flat spring member 18 is made with a relatively wide base 84 andnarrow end 85 as shown in Fig. 16, enlarged again at its outer end forthe purpose of receiving and holding stylus 33.

It should be noted that the point of the needle 33 is in substantialalignment with the plane of spring 18 when the weight of the pick-up ison the record, as indicated in dot and dash lines in Fig. 14. Thisminimizes the torsional forces upon the spring 18 and tends to decreaseits compliance in a horizontal plane. This also makes it possible toobtain maximum twisting effect on the crystal Where the forces from therecord are applied by the shank 15. Nevertheless, a large amount ofvertical compliance is permitted.

I Since substantial forces are exerted on the needle by reason of thetortuous character of the grooves and rapid changes in groove width-thattend to raise and lower the whole pick-up-this vertical compliance incooperation with the damping means acts as a mechanical lter to effect asubstantial diminution in high frequency noise, not only with respect tothat radiated acoustically but also that which is transmittedelectrically.

The base 84 of the spring member 18 may be enlarged so that it coincideswith the full surface of the bottom side of out-turned member 16, andopenings 80 may be holes instead of notches to fit over the bosses 11 ofmember 16. This strengthens the construction considerably.

In addition, the damping effect may be very considerably enhanced by theprovision of a bracing member 90 made of aluminum, magnesium, or somelight relatively sti metal alloy or other material. As illustrated, thisadditional damping member is constructed of a U shape as shown in Figs.14, 15 and 16, and the ends of the U are secured as by cementing orclamping them to the sides of the lobes 82 and 83 of the damping means8|. The mass of member 90 should be kept to a minimum. Tying the edgestogether strengthens the spread-out dampening member 8|, increases thedampening effect and reduces needle scratch and other undesirable highs.

Having thus described by invention, I claim:

l. In a sound translating device for use with sound disc records, thecombination of a floating pickup having a stylus secured thereto, a tonearm, means associated with said arm for securing said pickup entirely insuspension from said tone arm, said means comprising a pair of spacedtension cords made of acoustic damping material, one of said cordssecuring the front end of said pickup to said tone arm, the other ofsaid cords securing the back end of said pickup to said tone arm, andcounterbalancing means for leveling said tone arm to maintain said cordsin' tension, the gravitational turning moment of said pickup about anaxis transverse to the pickup at the point whereat said other cord issecured to said pickup being greater than the opposite moment producedby stylus pressure on a sound disc record.

2. In a sound translating device for use with sound disc records, thecombination of a floating pickup having a stylus secured thereto, a tonearm, a coupler associated with said arm for securing said 4pickupentirely in suspension from said tone arm, said coupler comprising apair of spaced tension means made of acoustic damping material, one ofsaid means securing the front portion of said pickup to said tone arm,the other of said means securing the back portion of said pickup to saidtone arm, counterbalancing means for leveling said tone arm to maintainsaid means in tension, the gravitational turning moment of said pickupabout an axis transverse to the pickup at the point whereat said othermeans is secured to said pickup being greater than the opposite momentproduced by stylus pressure on a sound disc record.

CHARLES E. KILGOUR.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,165,288 Rimmer Dec. 2l, 19151,281,135 Claybrook Oct. 8, 1918 1,325,209 Sandell Dec. 16, 19191,529,427 Giselman Mar. 10, 1925 1,721,362 Weir July 16, 1929 1,728,800Robinson Sept. 11, 1929 2,174,692 Dunning Oct. 3, 1939 2,187,772 DallyJan'. 23, 1940 2,230,865 Hutter Feb. 4, 1941 2,210,902 Rubissow Jan. 27,1942 2,313,129 Dohan Mar. 9, 1943 2,320,416 Dally June 1, 1943 2,331,122Jones Oct. 5, 1943 FOREIGN PATENTS Number Country Date 64,045 DenmarkOct. 22, 1945

